Inductively loaded folded antenna



Sept. 3, 1963 E. w. SEELEY 3,103,011

INDUCTIVELY LOADED FOLDED ANTENNA Fild Sept. 18, 1961 FIG. 2

ELWIN W. SEELEY INVENTOR.

BY 2 M 4 M ATTORNEY United States Patent INDUCTWELY LOADED FOLDED ANTENNA Elwin W. Seeley, Riverside, Calih, assignor to the United States of America as represented by the Secretary of the Navy Filed Sept. 18, 1961, Ser. No. 139,009 6 Claims. (Cl. 343--749) (Granted under Title 35, US. Code (1952), see. 266) The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to antennas and more particularly to an electromagnetic radiator in which the resonant radiation resistance may be varied over a wide range without increasing the radiator length.

Resonant antennas can be shorted by capacitive and inductive loading, however, the radiation resistance becomes small. Also, the folded dipole has high radiation resistance, but it must be one-half wavelength long.

The purpose of this invention is to radiate electromagnetic energy efficiently from a very short radiator, compared to a wavelength of the radiated energy, by means of a high resonant radiation resistance.

It is an object of the invention to provide a miniaturized electromagnetic radiator with increased resonant radiation resistance.

Another object of the invention is to provide an electromagnetic radiator in which the resonant radiation resistance can be varied over a wide range without increasing the radiator length.

A further object of the invention is to provide a loaded folded antenna wherein its resistance may be chosen over a 100 to 1 range without increasing its length.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIGURE 1 is a schematic diagram of an inductively loaded folded monopole antenna of the present invention.

FIGURE 2 is a schematic diagram showing capacity loading of the antenna, at the top thereof.

The inductively loaded folded antenna may be either a monopole or a dipole. in the case of the monopole antenna, as shown in FIGURE 1, two conductors 1t} and 12 are placed vertically above ground, spaced apart, and joined at the top by connector 14. Conductors 16 and 12 are broken about two-thirds of the distance to the top thereof and inductance coils 16 and 18, respectively, are inserted in series with the conductors, as shown, to provide lumped inductance in each conductor. Conductor 10, the grounded or folded conductor, is grounded to ground plane 20, and conductor 12 is fed, as an ordinary monopole would be fed, with a coaxial feed line 2-2, for example. The positioning of the coils can be anywhere along the conductors, however, the two-thirds from the grounded plane distance is optimum for the least amount of power loss.

The resonant length of the antenna can be adjusted by changing or varying the lumped inductance of coils 16 and 18 and their position in conductors lit and 12, and also the axial spacing S of the folded and driven con ductors and 12, respectively. The resonant radiation resistance of the antenna can be varied over a 100* to 1 ratio by changing the ratio of the diameters of the folded or grounded conductor 10* to the driven conductor 12. The radiation pattern for the antenna of the present invention will be essentially the same as that of an unloaded monopole. The inductively loaded folded monopole "ice herein disclosed can be loaded to a resonant length of .03 wavelength long, and with the resonant length remaining constant the resonant resistance can be varied from 20 to 200 ohms. Also, the resonant length of the present antenna can be one-eighth that of a resonant monopole of equal diameter.

In another embodiment, the antenna can be capacitively loaded as shown in FIGURE 2 by providing a plurality of spoke like elements 24 radiating outwardly from the end of ground conductor 10 or driven conductor 12 or anywhere along connector 14 which joins the ends of grounded conductor and the driven conductor.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An electromagnetic radiator in which the resonant radiation resistance can be varied over a wide range without increasing the radiator length comprising first and second parallel and spaced apart conductors mounted normal to a conductive ground plane and connected together at the opposite ends thereof from said ground plane by means of a third conductor, said first and second conductors each having an inductance coil in series therewith along the length thereof, the optimum position of said inductance coils along said first and second conductors for the least amount of power loss being a distance approximately two-thirds of the length of each conductor from its ground plane end, said first conductor being grounded to said ground plane and said second conductor being fed energy by means of a coaxial feed line connected thereto, the first conductor and the second conductor having difierent diameters and the resonant radiation of the antenna being variable by changing the ratio of the diameters of the first conductor to the second conductor.

2. An antenna in which the resonant length and resonant radiation can be varied comprising first and second parallel spaced-apart conductors mounted at one end thereof normal to a conducting ground plane and conductively connected together at the opposite end, said first and second conductors each having an inductance coil in series therewith along the length thereof for inductively loading said antenna, the optimum position of said inductance coils along said first and second conductors for the least amount of power loss being a distance approximately two-thirds of the length of each conductor from its ground plane end, said first conductor being grounded to said ground plane and said second conductor being driven by energy fed thereto by means of a coaxial feed line connected therewith, the grounded first conducto-r and the driven second conductor having different diameters and the resonant radiation of the antenna being variable over a to 1 ratio by changing the ratio of the diameters of the first conductor to the second conductor.

3. An antenna in which the resonant length and resonant radiation can be varied comprising first and second parallel spaced-apart conductors mounted at one end thereof normal to a conducting ground plane and conductively connected together at the opposite end, said first and second conductors each having an inductance coil in series therewith along the length thereof for inductively loading said antenna, the optimum position of said inductance coils along said first and second conductors for the least amount of power loss being a distance approximately two-thirds of the length of each conductor from its ground plane end, said first conductor being grounded to said ground plane and said second conductor being driven by energy fed thereto by means of a coaxial feed line connected therewith; the first conductor and the second conductor having difierent diameters and the resonant radiation of the antenna being variable by changing the ratio of the diameters of the first conductor to the second conductor, the resonant length of said antenna being adjustable by varying the value of the inductance coils, the distance the inductance coils are positioned from said grounded plane, and the axial spacing of said first and second conductors.

4. An antenna in which the resonant length and resonant radiation can be varied comprising first and second parallel spaced-apart conductors mounted at one end thereof normal to a conducting ground plane and conductively connected together at the opposite end, said first and second conductors each having an inductance coil in series therewith along the length thereof for inductively loading said antenna, the optimum position of said inductance coils along said first and second conductors for the least amount of power loss being a distance approximately two-thirds of the length of each conductor from its ground plane end, said first conductor being grounded to said ground plane and said second conductor being driven by energy fed thereto by means of a coaxial feed line connected therewith, the grounded first conductor and the driven second conductor having different diameters and the resonant radiation of the antenna being variable by changing the ratio of the diameters of the first conductor to the second conductor; the resonant length of said antenna being adjustable by varying the value of the inductance coils, the distance the inductance coils are positioned from said grounded plane, and the axial spacing of said first and second conductors.

5. A loaded foldedantenna in which the resonant radiation resistance can be varied over a wide range without increasing the antenna length, comprising a first and a second conductor mounted at one end thereof normal to a conductive ground plane and connected together at their opposite ends, said antenna being inductively loaded by means of said first and second conductors each having an inductance coil in series therewith along the length thereof, the optimum position of said inductance coils along said first and second conductors for the least amount of power loss being a distance approximately two-thirds of the length of each conductor from its ground plane end, said first conductor being grounded to said ground plane and said second conductor being fed energy by means of a feed line connected thereto, the first conductor and the second conductor having different diameters and the resonant radiation of the antenna being variable by changing the ratio of the diameters of the first conductor to the second conductor, said antenna being capacitively loaded by means of said opposite end of either of said first and second conductors having an array of a plurality of elements mounted thereon and extending radially outward therefrom in spoke-like form.

6. An antenna in which the resonant length and resonant radiation can be varied comprising first and second parallel spaced-apart conductors mounted at one end thereof normal to a conducting ground plane and conductively connected together at the opposite end, said first and second conductors each having an inductance coil in series therewith along the length thereof for inductively loading said antenna, the optimum position of said inductance coils along said first and second conductors for the least amount of power loss being a distance approximately two-thirds of the length of each conductor from its ground plane end, said first conductor being grounded to said ground plane and said second conductor being driven by energy fed thereto by means of a coaxial feed line connected therewith, the grounded first conductor and the driven second conductor having difierent diameters and the resonant radiation of the antenna being variable by changing the ratio of the diameters of the first conductor to the second conductor; the resonant length of said antenna being adjustable by varying the value of the inductance coils, the distance the inductance coils are positioned from said grounded plane, and the axial spacing of said first and second conductors; said antenna being capacitively loaded by means of said opposite end of either of said first and second conductors having an array of a plurality of elements mounted thereon and extending radially outward therefrom in spoke-like form.

References Cited in the file of this patent UNITED STATES PATENTS 2,495,399 Wheeler Jan. 24, 1950 2,998,604 Seeley Aug. 29, 196 1 FOREIGN PATENTS 220,059 Switzerland June 16, 1942 653,876 Great Britain May 30, 1951 

6. AN ANTENNA IN WHICH THE RESONANT LENGTH AND RESONANT RADIATION CAN BE VARIED COMPRISING FIRST AND SECOND PARALLEL SPACED-APART CONDUCTORS MOUNTED AT ONE END THEREOF NORMAL TO A CONDUCTING GROUND PLANE AND CONDUCTIVELY CONNECTED TOGETHER AT THE OPPOSITE END, SAID FIRST AND SECOND CONDUCTORS EACH HAVING AN INDUCTANCE COIL IN SERIES THEREWITH ALONG THE LENGTH THEREOF FOR INDUCTIVELY LOADING SAID ANTENNA, THE OPTIMUM POSITION OF SAID INDUCTANCE COILS ALONG SAID FIRST AND SECOND CONDUCTORS FOR THE LEAST AMOUNT OF POWER LOSS BEING A DISTANCE APPROXIMATELY TWO-THIRDS OF THE LENGTH OF EACH CONDUCTOR FROM ITS GROUND PLANE END, SAID FIRST CONDUCTOR BEING GROUNDED TO SAID GROUND PLANE AND SAID SECOND CONDUCTOR BEING DRIVEN BY ENERGY FED THERETO BY MEANS OF A COAXIAL FEED LINE CONNECTED THEREWITH, THE GROUNDED FIRST CONDUCTOR AND THE DRIVEN SECOND CONDUCTOR HAVING DIFFERENT DIAMETERS AND THE RESONANT RADIATION OF THE ANTENNA BEING VARIABLE BY CHANGING THE RATIO OF THE DIAMETERS OF THE FIRST CONDUCTOR TO THE SECOND CONDUCTOR; THE RESONANT LENGTH OF SAID ANTENNA BEING ADJUSTABLE BY VARYING THE VALUE OF THE INDUCTANCE COILS, THE DISTANCE THE INDUCTANCE COILS ARE POSITIONED FROM SAID GROUNDED PLANE, AND THE AXIAL SPACING OF SAID FIRST AND SECOND CONDUCTORS; SAID ANTENNA BEING CAPACITIVELY LOADED BY MEANS OF SAID OPPOSITE END OF EITHER OF SAID FIRST AND SECOND CONDUCTORS HAVING AN ARRAY OF A PLURALITY OF ELEMENTS MOUNTED THEREON AND EXTENDING RADIALLY OUTWARD THEREFROM IN SPOKE-LIKE FORM. 